Electric control apparatus



NOV. 1,7, 1931; lG. SOMAJNl 1,832,146

ELECTRIC CONTROL APPARATUS Filed Sept. 9, 1925 to2?l ground.

Patented Nov. 17, 1931 .PATENT vOFFICE GIACOMO SOMAJNI, OF MILAN, ITALYELECTRIC CONTROL APPARATUS Application led September 9, 1925, Serial No.55,299, and in Italy September 23g, 1924.

The present invention is directed to improvements in electro-magneticswitches.

The invention has for its object to obviate the drawbacks which theapparatus of this type have in their operation which could not bedetermined in some cases or which was affected by the oscillations ofthe movable member controlled by the antagonistic electromagnets.Finally, in order to obviate lo these drawbacks it is thereforenecessary to adopt suitable arrangements for ensuring a prompt,reliable, and decisive operation.

The movable member must be subject to a directing action which isexerted by the efect of gravity or by a suitable system of springs andreturns the said member to its position of rest when the electricactions cease. However, when the electrodynamic actions of theelectromagnets are eective the result of the S`0 said directing actionmust be such that the operation of the electromagnets is not affectedand the apparatus is permitted to operate practically in accordance withthe relations established between the aforesaid two antagonisticelectro-dynamic actions. Consequently, as soon as each of thee-lectromagnets enters into action, it must exert aconsiderableattraction on the movable member/'independently of the position occupiedby the said member andof the movements made by the latter; however, whenthe two electromagnets enter into antagonistic action, the twoattr-actions must be ractically vbalanced so as to leave the soledirecting action efficacious which tends toy maintain and to return themovable member to its position of rest.

A powerful and increasing action must be developed by each of theelectromagnets 40 when its action becomes preponderant so that themovable member is displaced and remains attracted by the prevailingelectromagnet without oscillation until the other electromagnet prevailsin its turn.

The members` effecting' the commutation are mounted on an oscillatinglever and they lead tothe result that the armatures, which 'are alsomounted on the same lever, are subjected to the act-:on of thecorresponding elec- 00 tromagnets. Each of these armatures has aprojection which forms a gap of Variable thickness with the ank of itselectromagnet which may be introduced in a wide gap formed in theelectromagnet.

These projections arefashioned and arranged n such a manner that in aremote position the end of the projection is situated exactly at theentrance of one of the said wide gaps between the-two members of thehorseshoe cores of the said electroma nets. lfVhen the armature isattracted towar s the electromagne-t, its corresponding projectionentersthe said gap which it almost completely occupies while leaving on itstwo sides two very small gaps; when finally the -armature has reachedits final position of attraction, a portion of the gap between themembers of the electromagnet core again remains empty beyond thecorresponding projection. It is possible to demonstrate by calculationand to verify by. experience that if the lateral gaps remaining on thetwo Hanks of the projection have a very small thickness withregard tothe total gap existing between the members of the electromagnet core,then the value of the attraction acting on each projection is greatlyincreased and it remains practically constant in all the positions whichthis projection may assume in accordance with the various positions ofthe' armature with which it is integral and moreover this attraction isgreater when the armature occupies its position which is more remotefrom the electromagnet., It follows therefrom that the presence of theprojections thus fashioned and arranged ensures a considerableattractive force on the remote armature, this force remainingconstanteduringt. the approaching movement with a slight tendency todlminish.

Moreover, the movable members integral with the eommutating members havethe said two well developed flanks opposite the surfaces suitably formedon the pole pieces of the electromagnets. Between each of these flanksand the corresponding pole piece there exists a gap which is wide whenthe armature is remote from the electromagnet and greatly reduced whenit is approached by the same; this gap varies quickly in proportion 'asthe armature is displaced opposite the said corresponding electromagnet.Conse uently, the attraction acting on each of the anks is very slightin the remote position and increases quickly during its course ofapproach in order to become extreme at the end of this course.

The result of these two attractions is consequently already extreme whenthe armature is in its remotest position from the correspondingelectromagnet on account of the projection and increases during thecourse of approach so that in all positions of the movable lever itsvalue is very high from the beginning and always of a high order withregard to the directing action.

Further features of the invention will be described with reference tothe accompanying drawings in which Figure 1 is a detail of a preferredform;

Figure 2 is a diagrammatic represent-ation of a kind of cascadearrangement of Switches for short circuiting a resistance section bysection.

The switch consists of contacts 30 and3l, an armature 32 and opposedshunts and series coils 4 and 5. The terminal 31 of the armature isconnected to the series coil 5, and

one end of the switch coil 4 is grounded as at 22. i A

The conducting part 32 is mounted on an arm or lever 39 pivoted at 36and' carrying near its middle an iron armature 40. This amaturecomprises two more or less vertical projections 41 and two horizontalportions 42. The vertical projections 41 are adapted to slide within airgaps 43 in upper and lower electromagnets 38, 37 which are energizedrespectively by the coils 4 and 5 also shown in Figure 1.

The tractive force exercised on the projections 41 by the correspondingelectromagnets is kept almost constant in all positions of the Parmature by so dimensioning the iron circuit of the electromagnets thateven in the limiting upward and downward positions of the projections 41the iron is not saturated.

The tractive force on the projections 41, however, increases rapidly asthey approach their respective magnets.

If, therefore, both 'the magnets are energized when the arm 39 is in itslower position 'the said arm will commence to rise when the tractiveforce of the upper electrolnagnet 38 predominates and will acceleraterapidly until it comes to rest against the upper magnet.

As will be seen in Figure 1, the arm 39 has beyond the pivot 36 a shorttail portion which connects or disconnects contacts 33 and 34 by meansof the conducting piece 35 acf cordingto whether the arm is in its upperor lower positions respectively. The purpose of this device will beexplained with regard citito the arrangement of Figure 2.

E1gure2 shows three switches, similar in constructionto that alreadydescribed with reference to Figure 1 except for the fact that the lastrelay has no tail and contact 35.

The saine reference figures have been used for all three relays withdistinguishing dashes.

The connections are,v as follows The three coils 5', 5 and 5 areconnected in series between the contact 15 oxra controller, not shown,and the commonfjunction of the contact 31 and the end of. R. The contact30 is connected to 31 and to the common junction of R and R.

Contact 30 is connected to 31 and the common junction of R and R".

Contact 30" is connected to the remaining end of R.

The coil 4 is connected across the terminals 22 and 14 as in Fi ures 1and 2 and by means of the tail ends o the arms 39 and 39 the coils 4 and4 are connect-cd in sequence across the same terminals, viz. 22, orground and 14 when the arms 39 and 39 rise in sequence and connectsuccessively 33 to 34' and33 to 34".

In operation the first switch operates an( short clrcuits indue coursethe resistance R; at the same time the coil 4" is energized by thecompletion of the circuit through 33 and 34 and the second relayoperates to short circuit the resistance R and energize in turn the coil4 of the third relay which thereupon short circuits the remainingresistance R Y Having now described my invention, what I claim as newand desire to secure by Let.- ters Patent is y An electromagnetic switchcomprising a pivotally mounted armature having contacts thereon, saidarmature having a pair of opositelyextending rojections carried therey,a pair of spaced) cores each having a gap vositioned in operativerelation to said projections, an operating winding on one of said coresfor attracting one of saidprojections into one of the ga s, arestraining winding on the other core r holding the other projection insaid gap until the current in said winding drops to a predeterminedvalue.

Signed at Milan, Italy, this 25th day of August, 1925. c GIACOMOSOMAJNI.'

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